1. Field of the Invention
The present invention relates to a camera system having a photographic camera and an electronic flash device for controlling the power supply to the camera or the electronic flash device. A control system for an electronic flash device, by way of example of the above camera system, is disclosed which comprises power supply start means for supplying electric power to operational devices of the electronic flash device such as a voltage boosting circuit and a display device by a starting operation by switching means provided in the electronic flash device or by an input of start signal provided outwardly of the electronic flash device such as an interval controller for controlling a photographic operation at certain intervals and a camera body and further comprises power supply stop means for stopping the power supply to the operational devices when a certain predetermined time period has passed since the above power supply start means starts the power supply.
2. Description of the Prior Art
In the photographic camera system having the electronic flash device, the control system therefor and the like, the more electronics or automation employed in the system results in a greater number of electrically driven devices. And such each device is provided with power source mostly by battery as the device need be formed compact. However, the capacity of the primary battery often used as the power source, especially that of a dry battery is limited. Therefore, in order to minimize power consumption in the battery, there are various improvements provided in the circuit construction and the like of the respective operational devices.
Also, there is disclosed prior art to achieve the above object by eliminating wasteful power consumption resulting when the operational devices are out of operation or when the main switch is left turned `ON` mistakenly. The electronic flash device is also provided with such a known construction wherein the power supply to the operational devices is automatically stopped or terminated when a predetermined time period (will be referred to as power supply hold time hereinafter) has passed since the main switch is turned `ON`, for instance. Further, a Japanese utility model application published or laid open for public inspection under No. 59-176025 discloses art wherein a setting time change switch is provided for varying the above power supply hold time.
However, this known construction has the following disadvantages and therefore need be improved.
Particularly, if a relatively long time period is set, a quick photographic operation is possible since the electronic flash device is always ready for a light emission operation during the set time period, however, this results in a greater power consumption. That is to say, the voltage boosting circuit is repeatedly turned `ON` and `OFF` in order to maintain a voltage in a main capacitor for charging a flash light energy higher than the level required for the light emission. This frequent turning `ON` and `OFF` of the boosting circuit entails at its each initial stage great power consumption thereby to quickly shorten the life of the battery.
On the other hand, if a relatively short time period is set, the power consumption of the battery is restricted; however, if the power supply hold time is just completed when an operator desires to take a flash photography, the operator needs to restart the boosting operation of the electronic flash device thus he may miss a shutter change because this restarting operation requires charging time to the main capacitor.
Furthermore, in the case of the photographic camera system having the internal controller for automatically carrying out the interval photography by operating the camera body and its accompanying peripherals such as an electronic flash device at certain intervals, there are problems to be described next.
When the operation of the camera body is controlled by the interval controller, the photographic operation is carried out at certain intervals but is rarely carried out between the intervals. However, as long as the power supply hold time, the electronic flash device is kept always ready for operation, whereby, as described hereinbefore, great amount of power is consumed and the life of the battery is shortened.